Bug 37797: Change cancel button to a link styled as a button

Bug 37797: Change cancel button to a link styled as a button

On the confirmation page for deleting a budget, change "Do not delete"
from a form submission to a link (styled to look like a button) in order
to avoid errors from POSTing with no op.

To test:
1. Go to Acquisitions > Budgets
2. Create a test budget
3. Attempt to delete the test budget
4. On the confirmation page, click "No, don't delete"
--> An error appears saying that the form was POSTed with no op!
5. Apply patch
6. Repeat steps 3-4
--> You are linked back to the Budgets page. The budget was not deleted.

Signed-off-by: Chloe Zermatten <chloe.zermatten@ptfs-europe.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>